The purpose of this project, entitled "Studies of Chemical Disposition in Mammals", is to procure chemical disposition studies to be performed in support of the toxicity and carcinogenicity studies conducted by the National toxicology Program (NTP). This program is designed to provide data on acute and chronic toxicity which may result from exposure to selected chemicals. The Contractor shall conduct 6-10 chemical disposition and toxicokinetic studies per year. The results of these studies provide the basis for predictions of bioaccumulation and toxicity and thereby enhance the accuracy of dose selection as well as improve the design of the animal bioassay program. Furthermore, chemical disposition and toxicokinetic studies provide information which will allow the NTP to establish the relationships between toxicity and bioavailability of chemicals and/or metabolites and permits a better extrapolation of laboratory data to humans. The contracts obtained under this project will continue the work under predecessor contracts N01ES65137 and N01ES65138.